In the past week we share here on the blog the news about the release of the first RC of what will be the next version of the Kernel Linux 5.12, which for this version 5.12-rc1, Linus Torvalds named it Frozen Wasteland, because it started with winter ice storms in the Portland area that cut down thousands of trees and deprived a quarter of a million people of more power.
For six days, Linus also found himself without power, which prevented him from working on the new fusion window. But after this first week marred by the vagaries of the weather, Linus was able to catch up on the backlog and announced the release of Linux 5.12-rc1 in late February as planned.
In this first Linux 5.12 release candidate, emphasis has been placed on cleaning up the code, such as OPROFILE support, Intel MID support, Intel Simple Firmware Interface support, some old and outdated ARM platforms, several drivers that have been removed. Alongside this historic cleanup, many additions have also been made. We have, among others, support for Intel ASIC N5X and Snapdragon 888 platforms, better support for Microsoft Surface devices, integration of various x86 drivers, support for Adreno 508/509/512 GPUs in MSM, support for SiFive FU740 and HiFive Unmatched RISC- Cards. V, adding NUMA support for RISC-V, overclocking support for AMD Radeon RX 6800/6900 series GPUs, etc.
After announcing the Linux 5.12-rc1 release at the end of last month, Linus made a second pitch a few days ago to advise against the use of this launch candidate. To be heard, he renamed this version to "v5.12-rc1-dontuse" in your git tree to warn users what to do with this version.
Linus explains that a code simplification and cleanup was done in Linux 5.12-rc1 where no alerts were generated. However, this resulted in:
"A very nasty and subtle bug in which paging files have stopped working properly, stopped working in a particularly bad way: the offset of the start of the swap file was lost."
Normally, errors caused by code changes are automatically detected, but the paging code is different, since "paging files are not normal". He adds that he doesn't blame the developers who were supposed to catch these kinds of bugs, noting that it wasn't due to the weird timing of the merge window either. For him, this was simply an unusual bug that was detected and isolated in the current tree.
Linus clarifies that if this latest experimental version is used, you could end up with a filesystem which is essentially overwritten with random swap data. The good news is that, in general, many distributions by default change partitions instead of exchanging files. But Ubuntu, which is one of the most widely used Linux distributions, has been installing swap files by default for over four years. For users of Ubuntu (or derived distributions like Mint), this warning from Linus is more than timely, because using this latest version of the kernel there is a high probability that this error will destroy the entire file system.
In addition to this issue that could affect distributions that use paging files, Linus explains that he added the "dontuse" tag in his public git tree so that people aren't tempted to start a new branch. Kernel since this latest version. Usually all goes well with the release candidates, but this time Linus recommends against using it as it might work fine on a system that uses a swap partition, but ends badly for systems that use a swap partition.
Finally, if you are interested in knowing more about the news that Linus Torvalds announced, you can consult the details In the following link.
The good news is that, in general, many distributions by default change partitions instead of exchanging files.
Don't you mean?
Many distributions use swap partitions instead of memory swap files.